The Bolivar Police Department said Lammers' mother called authorities Thursday with concerns that her son had bought weapons similar to those in the Aurora massacre and that he might be planning a movie theater shooting, the News-Leader reported.

Police then interviewed Lammers, who reportedly said he purchased two assault rifles for hunting and that he had also bought 400 rounds of ammunition, the newspaper added.

A probable cause statement prepared by the Bolivar Police Department stated that Lammers had also purchased tickets to see the new "Twilight" movie and was planning to shoot people at the theater, the Bolivar Herald-Free Press reported.

The police statement added that Lammers thought he might run out of ammunition, so he decided to instead shoot people at a Walmart store in Bolivar.

A town of around 10,000 people, Bolivar is about 130 miles southeast of Kansas City, according to The Associated Press.

Bolivar Police Department Detective Dusty Ross told the Herald-Free Press the he doesn't believe anyone else was involved in the plot, but that "(Lammers) had taken every step he needed to take except for actually committing the act."

"Everything is taken care of," Bolivar City Administrator Darin Chappell told the newspaper. "There's no need to be alarmed."

Police say Lammers was familiar with high profile shootings in the news and allegedly planned something similar in 2009, the Herald-Free Press reported.

"Thankfully we had a responsible family member or we might have had a different outcome," Bolivar Police Chief Steve Hamilton told the AP. He said Lammers is under a doctor's care for mental illness, and court documents said he was "off of his medication," the AP reported.

Authorities are still investigating the case, while Lammers remains in jail on a $500,000 bond, according to the Herald-Free Press.